In the oil and gas exploration and production industry, subsurface hydrocarbon-bearing rock formations are accessed by drilling bores from surface, which bores are subsequently lined with metal tubing, known as casing or liner. During the drilling of the bore, and in many subsequent operations, drill bits or other tools are positioned in the bore on the end of an elongate tubular support, which may be sectional drill pipe or coiled tubing, for example. In many cases, fluid is pumped through the support, and this fluid may serve a number of different functions. In a drilling operation, the fluid may exit the drill pipe string through jetting nozzles at the drill bit, the jets of fluid assisting in dislodging material from the cutting face. The drilling fluid then assists in carrying the cuttings to surface. The fluid may also be used as a means to actuate tools, for example by providing flow restrictions in the bore or by use of differential pistons.
It is among the objectives of embodiments of the present invention to enhance the operation of downhole tools which, at least to some extent, utilise fluid in their operation.